Wind power plant with a particle sensor

ABSTRACT

Wind power installations using more modern technology have long been known. Such wind power installations have rotors comprising at least one or more rotor blades. The rotors and accordingly the rotor blades carried thereby of wind power installations are subjected to a particular degree to the ambient environmental influences such as for example rain, snow, hail or also insects. In particular the leading edges of the rotor blades are heavily loaded in that respect. In that situation it can happen that the rotor blades and in particular the leading edges thereof, after some time, suffer from (mechanical) damage, for which cost-intensive repair is necessary, especially as a crane is frequently required for that purpose and the entire wind power installation is also stopped for a prolonged period due to the repair and under some circumstances even individual rotor blades have to be transported away to the repair location.  
     The object of the present invention is to reduce the erosion damage at the rotor blades and to avoid the above-mentioned disadvantages.  
     A method of operating a wind power installation having at least one sensor for detecting the number and/or the speed and/or the impulse of particles which impinge on the sensor, with a data processing and control device for processing the measurement data detected by the sensor, wherein the rotary speed of the rotor of the wind power installation is reduced (by means of the data processing/control device) and/or the wind power installation is stopped if a particle measurement value measured by the sensor is exceeded.

[0001] Wind power installations using more modern technology have long been known. Such wind power installations have rotors comprising at least one or more rotor blades. The rotors and accordingly the rotor blades carried thereby of wind power installations are subjected to a particular degree to the ambient environmental influences such as for example rain, snow, hail or also insects. In particular the leading edges of the rotor blades are heavily loaded in that respect. In that situation it can happen that the rotor blades and in particular the leading edges thereof, after some time, suffer from (mechanical) damage, for which cost-intensive repair is necessary, especially as a crane is frequently required for that purpose and the entire wind power installation is also stopped for a prolonged period due to the repair and under some circumstances even individual rotor blades have to be transported away to the repair location.

[0002] Such damage is to be attributed to erosion effects which damage the surface—the so-called gel coat—of the rotor blades, which as the counterpart results in a worsening of the aerodynamic properties of the blades.

[0003] The object of the present invention is to reduce the erosion damage at the rotor blades and to avoid the above-mentioned disadvantages.

[0004] In accordance with the invention that object is attained by a method having the features of claim 1 and a wind power installation for carrying out the method as set forth in claim 4. Advantageous developments are described in the appendant claims.

[0005] The strength of the influence of weather conditions such as rain, snow, hail or also insects on the rotor blade leading edge is substantially dependent on the rotary speed of the wind power installation. The faster the blades are rotating, the correspondingly higher is the speed of the rotor blade tip and the correspondingly greater is the impingement speed of particles such as for example raindrops, hailstones, snowflakes, insects or even grains of dust—referred to hereinafter generally as particles—against the rotor blade.

[0006] Wind power installations in accordance with the state of the art are generally operated with given operating characteristics, irrespective of the weather. In the case of installations with a variable rotary speed—such as for example the wind power installations from Enercon of type E-40 or E-66 et al—that signifies for example a given installation-typical rotary speed-power characteristic.

[0007] In the case of the wind power installations nowadays—of the above-mentioned type—of the order of magnitude of between 500 kW and 1.5 MW, the maximum blade tip speeds are in the range of 65-75 m/s or corresponding to 234-270 kph.

[0008] The invention is based on the realisation that the greatest erosion damage is caused at the rotor blade leading edge by particles which impact against the rotor blade leading edge.

[0009] In accordance with the invention it is now proposed that a wind power installation be equipped with one or more sensors which can detect the respective (wind-independent) weather conditions and give corresponding signals to the wind power installation control system which suitably reacts thereto by reducing the rotary speed of the rotor of the installation for example in heavy rain—that is to say with a high number of particles within a predetermined unit of time (for example within a minute).

[0010] The method according to the invention and the wind power installation according to the invention make it possible to avoid or drastically reduce weather-induced erosion damage to the wind power installation. That in turn results in a reduction in expensive rotor blade repairs and in addition the fact of keeping the surfaces of the rotor blades intact can afford a uniform level of efficiency of the wind power installation. The invention is described in greater detail hereinafter by means of an embodiment.

[0011] The Figure is a diagrammatic view showing a wind power installation 3 having a rotor 4 which comprises three rotor blades 5. Mounted on the rotor blade hub 4 and/or at the rotor blades 5 (the leading edge) are sensors 1, 2 which measure there the incidence against the sensor of particles which are borne on the wind to the wind power installation. The sensor or sensors are connected to a data processing device 6 (PC) of the wind power installation, which evaluates the measured data and sets for example a suitable amount/time ratio, that is to say, detects the number of particles over a given period of time. If more than a predetermined number of particles, for example 10-20 particles (raindrops) impinge on a sensor within a given unit of time, for example 5-10 seconds, the rotary speed of the wind power installation is reduced by means of a program stored in the data processing device. That admittedly also results in a reduction in the total power which the wind power installation produces. As however the rainy times are usually relatively short in comparison with the periods which are free from precipitation, that is scarcely significant and it is possible to provide for effective protection for the rotor blades if the rotary speed thereof is reduced, for example halved, during the precipitation periods.

[0012] It will be appreciated that the data processing device also processes as usual the measured wind data which are measured with other sensors and causes a reduction in the rotary speed of the rotor only when the wind speed exceeds a predetermined value.

[0013] It is also possible by means of the data processing device to effect measurement of the particle amount, particle speed and/or particle impulses (the so-called precipitation energy), that is to say the precipitation power (amount of precipitation (particles), speed of the precipitation) can be detected (integrated) over a given period of time and the reduction in the rotary speed is initiated when the precipitation energy or precipitation power exceeds a predetermined value.

[0014] It is also possible by means of the sensors to measure an addition or integration of the impulses (mass of a particle multiplied by the impingement speed of the particle).

[0015] If the impulses caused by particles exceed a predetermined value in respect of their magnitude, a reduction in rotary speed is automatically effected so that this also automatically results in a reduction in the impulse forces on the rotor blades, caused by the precipitations. 

1. A method of operating a wind power installation having at least one sensor for detecting the number and/or the speed and/or the impulse of particles which impinge on the sensor, with a data processing and control device for processing the measurement data detected by the sensor, wherein the rotary speed of the rotor of the wind power installation is reduced (by means of the data processing/control device) and/or the wind power installation is stopped if a particle measurement value measured by the sensor is exceeded.
 2. A method according to claim 1 characterised in that the rotary speed of the wind power installation is reduced and the wind power installation is stopped if a given number of particles has been measured by the sensor within a given period of time.
 3. A method according to one of the preceding claims characterised in that water drops (raindrops) and/or hailstones and/or grains of dust are measured as particles.
 4. A wind power installation for carrying out the method according to one of the preceding claims comprising at least one sensor for detecting the number, the energy and/or the impulse of particles which impinge on the sensor, wherein the sensor is connected to a data processing and control device which processes measurement data ascertained by the sensor and reduces the rotary speed of the wind power installation and optionally stops the wind power installation when a predetermined particle measurement value is exceeded.
 5. A wind power installation according to claim 4 characterised in that the wind power installation has a plurality of sensors for measuring particles.
 6. A wind power installation according to one of claims 4 and 5 characterised in that the sensor or the plurality of sensors is or are arranged at or on the rotor blades of the wind power installation.
 7. A wind power installation according to one of claims 4 to 6 characterised in that a sensor detects the number of impinging particles (per time) and/or the impingement speed of particles against the sensor and/or the impulse value of impinging particles.
 8. A wind power installation according to one of claims 4 to 7 characterised in that the sensor is arranged at the leading edge of a rotor blade of the wind power installation.
 9. A wind power installation according to claim 8 characterised in that at least one sensor is arranged in the region of the rotor blade tip or another region of the wind power installation, for example the pod. 